| 1 | HY | European Airways Ltd. | ICAO: EAW, Callsign: European, | GB | AVCODES |
| 2 | HY | Henry Nielsen, Oy, Ab. | Callsign: Henrynielsen, | FIN | AVCODES |
| 3 | HY | Hala Air | ICAO: HTP, Callsign: Hala Express, IATA Designator chnaged to HG. | LAR | AVCODES |
| 4 | HY | Uzbekistan Airways Joint Stock Company | ICAO: UZB, Callsign: Uzbek, IATA Prefix: 250, Name changed from Uzbekistan Havo Yullary - Uzbekistan Airways. | UZ | AVCODES |
| 5 | HYA | Hyack Air (1981) Ltd. | Callsign: Hyack, | CDN | AVCODES |
| 6 | HYA | Al-Haya Aviation | IATA: HA, Callsign: Alhaya, IATA Prefix: 164, | IRQ | AVCODES |
| 7 | HYA | Hyack Air | | | ICAO1 |
| 8 | HYAJ | HYATT, JIM PRODUCE CO INC | | | SCAC4 |
| 9 | HYAP | HYDRA TRANSPORTATION | | | SCAC4 |
| 10 | HYAR | HILLYARD FARMS | | | SCAC4 |
| 11 | HYAT | HYBRID TRANSIT SYSTEMS INC | | | SCAC4 |
| 12 | HYAU | PETROCHEMICA | | | SCAC4 |
| 13 | HYBB | HOLIWAY TRANSPORT | | | SCAC4 |
| 14 | HYBD | HYBUR LTD | | | SCAC4 |
| 15 | HYBE | HYBELS, BERT R INC | | | SCAC4 |
| 16 | HYBH | HARDY BROTHERS INC | | | SCAC4 |
| 17 | HYBI | HYBRID INTERMODAL TRANSPORTATION LL | | | SCAC4 |
| 18 | HYBL | HYBRID LOGISTICS INC | | | SCAC4 |
| 19 | HYBM | HAPPY BURRITO, THE | | | SCAC4 |
| 20 | HYBS | HONEYCOMB MAILING SERVICES LIMITED | | | SCAC4 |
| 21 | HYBU | HYBUR LTD | | | SCAC1 |
| 22 | HYBU | HYBUR LTD | | | SCAC4 |
| 23 | HYC | Hydro Air (PTY) Ltd. | Callsign: Hydro Cargo, | ZA | AVCODES |
| 24 | HYC | Hydro Air Flight Operations | | | ICAO1 |
| 25 | HYCB | HYMARK EXPRESS INC | | | SCAC4 |
| 26 | HYCC | HAPPY YELLOW CHECKER CAB | | | SCAC4 |
| 27 | HYCD | HAYCOCK DISTRIBUTING CO INC | | | SCAC4 |
| 28 | HYCI | HAY, CLIFFORD C INC | | | SCAC4 |
| 29 | HYCK | HAY CREEK EXPRESS INC | | | SCAC4 |
| 30 | HYCM | HYDRO CHEM INDUSTRIAL SERVICES INC | | | SCAC4 |
| 31 | HYCO | HUSKEY BUS & TRANSPORTATION SERVICE | | | SCAC4 |
| 32 | HYCQ | HOMETOWN ENERGY LLC | | | SCAC4 |
| 33 | HYCT | HUNEYCUTT TRANSPORT | | | SCAC4 |
| 34 | HYCW | HAYWORTH, C & V TRUCKING CO | | | SCAC4 |
| 35 | HYD | Hydro-Quebec | IATA: 0Q, Callsign: Hydro, Designator 0Q* recalled by IATA. | CDN | AVCODES |
| 36 | HYD | Hydro-Quebec | Callsign: Hydro, Designator 0Q* recalled by IATA. | CDN | AVCODES |
| 37 | HYD | Hydro-QuA~©bec | | | ICAO1 |
| 38 | HYDA | HYDER TRANSPORTATION LLC | | | SCAC4 |
| 39 | HYDB | HYDER BOYS TRANSPORT LLC | | | SCAC4 |
| 40 | HYDC | HAYDEN TRANSPORTATION LLC | | | SCAC4 |
| 41 | HYDD | HIGIENICOS Y DESECHABLES DEL BAJIO | | | SCAC4 |
| 42 | HYDG | HYDE, GENE TRUCKING CO INC | | | SCAC4 |
| 43 | HYDK | HAYDUK ENTERPRISES INC | | | SCAC4 |
| 44 | HYDL | HYDE, GENE LOGISTICS INC | | | SCAC4 |
| 45 | HYDN | HAYDEN TRANSPORT INC | | | SCAC4 |
| 46 | HYDP | HYDRO TECHNOLOGIES (CANADA) INC | | | SCAC4 |
| 47 | HYDR | HYDRAULICS UNLIMITED | | | SCAC4 |
| 48 | HYDR | Hydrema Baumaschinen GmbH | | DE | VKM |
| 49 | HYDS | HYDROUSSA SHIPPING CO. S A | | | SCAC4 |
| 50 | HYDU | XINJIANG HONGYUNDA FREIGHT INTERNATIONAL CO., LTD. | | PRC | BIC |
| 51 | HYDU | HYDE SHIPPING | | | SCAC1 |
| 52 | HYDU | Hyundai | | | SCAC2 |
| 53 | HYDU | AMPHIBIOUS CONTAINERS LEASING LTD | | | SCAC4 |
| 54 | HYDX | Praxair, Inc. | added 1/1993; 1/1994-7/2005 | | NAKINA |
| 55 | HYDX | Union Carbide Corp., Chemicals and Plastics Co., Inc. | eliminated 1/1993 | | NAKINA |
| 56 | HYDX | Union Carbide Corp. | added 5/1983 | | NAKINA |
| 57 | HYDX | Union Carbide Corp., Chemicals and Plastics Co., Inc. | eliminated 5/1983 | | NAKINA |
| 58 | HYDX | Union Carbide Corp., Chemicals and Plastics Division | added 10/1980 | | NAKINA |
| 59 | HYDX | Union Carbide Corp., Chemicals and Plastics Co., Inc. | added 7/1980 | | NAKINA |
| 60 | HYDX | Union Carbide Corp. | eliminated 10/1980 | | NAKINA |
| 61 | HYDX | Union Carbide Corp., Chemicals and Plastics Co., Inc. | added 7/1980 | | NAKINA |
| 62 | HYDX | Union Carbide Corp., Chemicals and Plastics Division | added 1/1979; 1/1980; eliminated 7/1980 | | NAKINA |
| 63 | HYDX | Union Carbide Corp., Chemicals and Plastics Operations Division | added 1/1968; 4/1970-1/1975; eliminated 1/1979 | | NAKINA |
| 64 | HYDX | Union Carbide Corp., Chemicals and Plastics | added 10/1967; eliminated 1/1968 | | NAKINA |
| 65 | HYDX | Union Carbide Corp., Chemicals Division | added 7/1961; 7/1965-10/1966; eliminated 10/1967 | | NAKINA |
| 66 | HYDX | Union Carbide Corp., Chemicals Division | 7/65-10/66; eliminated 10/67 | | NRHS |
| 67 | HYDX | Union Carbide Corp., Chemicals and Plastics | added 10/67; eliminated 1/68 | | NRHS |
| 68 | HYDX | Union Carbide Corp., Chemicals and Plastics Operations Division | added 1/68; 4/70-1/75; eliminated 1/79 | | NRHS |
| 69 | HYDX | Union Carbide Corp., Chemicals and Plastics Division | added 1/79; 1/80; eliminated 7/80 | | NRHS |
| 70 | HYDX | Union Carbide Corp., Chemicals and Plastics Co., Inc. | added 7/80 | | NRHS |
| 71 | HYDX | Union Carbide Corp. | eliminated 10/80 | | NRHS |
| 72 | HYDX | Union Carbide Corp., Chemicals and Plastics Co., Inc. | added 7/80 | | NRHS |
| 73 | HYDX | Union Carbide Corp., Chemicals and Plastics Division | added 10/80 | | NRHS |
| 74 | HYDX | Union Carbide Corp., Chemicals and Plastics Co., Inc. | eliminated 5/83 | | NRHS |
| 75 | HYDX | Union Carbide Corp. | added 5/83 | | NRHS |
| 76 | HYDX | Union Carbide Corp., Chemicals and Plastics Co., Inc. | eliminated 1/93 | | NRHS |
| 77 | HYDX | Praxair, Inc. | added 1/93; 1/94-7/2000 | | NRHS |
| 78 | HYDX | (UCOX) PRAXAIR, INC. [UNION CARBIDE CORP.] | | | PWRC |
| 79 | HYDX | Union Carbide Corporation (Praxair) | | | RSRV |
| 80 | HYDX | PRAXAIR, INC. | | | SCAC4 |
| 81 | HYE | Hyeres Sero Service | Callsign: Hyero, | F | AVCODES |
| 82 | HYEC | HAYLES EXPRESS CARRIER | | | SCAC4 |
| 83 | HYED | HARDY, EDWIN TRUCKING INC | | | SCAC4 |
| 84 | HYEG | HERRERA, YEGUADA | | | SCAC4 |
| 85 | HYES | HAYES, STEPHEN | | | SCAC4 |
| 86 | HYFA | HERBTHYME FARMS | | | SCAC4 |
| 87 | HYFC | HYDE FUEL CO | | | SCAC4 |
| 88 | HYFM | HYMAN FARMS TRUCKING | | | SCAC4 |
| 89 | HYGR | HYGRID LOGISTICS INC | | | SCAC4 |
| 90 | HYGX | North American Car Corp. | 4/1947-7/1965; eliminated 10/1965 | | NAKINA |
| 91 | HYGX | North American Car Corp. | 1/52-7/65; eliminated 10/65 | | NRHS |
| 92 | HYGX | NORTH AMERICAN CAR CORP. | | | PWRC |
| 93 | HYH | Heli Hungary Ltd. | Callsign: Helihungary, | H | AVCODES |
| 94 | HYH | Heli Hungary | | | ICAO1 |
| 95 | HYHI | HAILEYS HAULING INC | | | SCAC4 |
| 96 | HYHY | HAYES & HAYES TRUCKING INC | | | SCAC4 |
| 97 | HYIL | HYATT INDUSTRIES LIMITED | | | SCAC4 |
| 98 | HYJ | Happy Jet Co., Ltd. | Callsign: Happy Jet, | PRC | AVCODES |
| 99 | HYJA | HAYNES, JOHN A TRUCKING | | | SCAC4 |
| 100 | HYJC | HURLEY, J C | | | SCAC4 |